Algae biofertilisers promote sustainable food production and a circular nutrient economy - An integrated empirical-modelling study

Zeenat Rupawalla; Nicole Robinson; Susanne Schmidt; Sijie Li; Selina Carruthers; Elodie Buisset; John Roles; Ben Hankamer; Juliane Wolf

doi:10.1016/j.scitotenv.2021.148913

Algae biofertilisers promote sustainable food production and a circular nutrient economy - An integrated empirical-modelling study

Sci Total Environ. 2021 Nov 20:796:148913. doi: 10.1016/j.scitotenv.2021.148913. Epub 2021 Jul 10.

Authors

Zeenat Rupawalla¹, Nicole Robinson², Susanne Schmidt², Sijie Li², Selina Carruthers², Elodie Buisset¹, John Roles¹, Ben Hankamer¹, Juliane Wolf³

Affiliations

¹ Institute for Molecular Bioscience, The University of Queensland, Brisbane, Queensland 4072, Australia.
² School of Agriculture and Food Science, The University of Queensland, Brisbane, Queensland 4072, Australia.
³ Institute for Molecular Bioscience, The University of Queensland, Brisbane, Queensland 4072, Australia. Electronic address: j.wolf@imb.uq.edu.au.

PMID: 34328895
DOI: 10.1016/j.scitotenv.2021.148913

Abstract

Agriculture has radically changed the global nitrogen (N) cycle and is heavily dependent on synthetic N-fertiliser. However, the N-use efficiency of synthetic fertilisers is often only 50% with N-losses from crop systems polluting the biosphere, hydrosphere and atmosphere. To address the large carbon and energy footprint of N-fertiliser synthesis and curb N-pollution, new technologies are required to deliver enhanced energy efficiency, decarbonisation and a circular nutrient economy. Algae fertilisers (AF) are an alternative to synthetic N-fertiliser (SF). Here microalgae were used as biofertiliser for spinach production. AF production was evaluated using life-cycle analyses. Over 4 weeks, AF released 63.5% of N as bioavailable ammonium and nitrate, and 25% of phosphorous (P) as phosphate to the growth substrate; SF released 100% N and 20% P. To maximise crop N-use and minimise N-leaching, we explored AF and SF dose-response-curves with spinach in glasshouse conditions. AF-grown spinach produced 36% less biomass than SF-grown plants due to AF's slower and linear N-release; SF exhibited 5-times higher N-leaching than AF. Optimised AF:SF blends yielded greater synchrony between N-release and crop-uptake, boosting crop yields and minimising N-loss. Additional benefits of AF included greener leaves, lower leaf nitrate concentration, and higher microbial diversity and water holding capacity of the growth substrate. An integrated techno-economic and life-cycle-analysis of scaled-up microalgae systems (+/- wastewater) normalised to the application dose showed that replacing the most effective SF-dose with AF lowered the annual carbon footprint of fertiliser production from 3.644 kg CO₂ m^-2 (C-producing) to -6.039 kg CO₂ m^-2 (C-assimilation). N-loss from growth substrate was lowered by 54%. Embodied energy for AF:SF blends could be reduced by 29% when cultivating microalgae on wastewater. Conclusions: (i) microalgae offer a sustainable alternative to synthetic N-fertiliser for spinach production and potentially other crop systems, (ii) microalgae biofertilisers support the circular-nutrient-economy and several UN-Sustainable-Development-Goals.

Keywords: Bioeconomy; Decarbonisation; Impact indicator analysis; Microalgae; Nitrogen use efficiency; Spinach growth.

MeSH terms

Biomass
Fertilizers* / analysis
Microalgae*
Nitrogen
Nutrients
Wastewater

Substances

Fertilizers
Waste Water
Nitrogen